For both home and commercial growers alike, managing garden space while maximizing yields can be a difficult task. This is especially true in urban areas, where the demand for marijuana is high—but so are the costs associated with renting, buying or building indoor space for cannabis cultivation.

For decades, the indoor horticulture industry has looked for ways to best utilize indoor garden space to maximize yields. Whether it be the giant flower farms of Holland, the sprawling vegetable greenhouses of Canada or the massive indoor commercial cannabis operations in the United States, many indoor growers are using vertical grow formats, whose popularity has been on the rise over the past few years with a new demographic: home growers.

System Types

Vertical grow systems are typically not do-it-yourself or build-your-own systems. Rather, commercially available vertical systems are purchased from hydroponic shops or wholesale distributors and then modified to the grower’s specific needs and space. Just like typical horizontal or flatbed grow systems, vertical grow systems can be used with almost any type of indoor grow technique, from hydroponics and aeroponics to soilless-medium methods. The latter is the least likely example one might find, though, as the weight of soil mediums—as well as the sheer volume—can make for cumbersome maintenance, less flexibility and lower functionality (more on this in a bit).

In traditional vertical grow systems, lights are hung vertically, usually on chains, with the plants placed around them in a cylindrical arrangement from floor to ceiling. A primary benefit of this arrangement is a better utilization of light, both in terms of energy efficiency and light absorption, by the encompassing plant canopy. The removal of reflectors creates a direct path for light energy, or photons, from bulb to plants and eliminates the conversion of light into heat that occurs when photons bounce off reflectors or are otherwise absorbed elsewhere and not by the plants. Additionally, when the vertical string of lights in these systems is adequately cooled (either by air-cooling tubes, water jackets or AC units), the plant canopy can sit within inches of the lights, thereby increasing the energy delivered to the plants.

While most vertical grow systems utilize this cylindrical arrangement to take better advantage of light placement and full photon absorption, alternatives to grow cylinders are becoming more popular, especially in large-format grows. Vertical rack systems are frequently used as commercial indoor growers look for lightweight, stackable grow systems that can deliver water and nutrients to plants quickly and effectively. These vertical grow systems mimic smaller horizontal hydro systems that can be stacked one on top of another from floor to ceiling with the required lighting placed in between each stackable tray or plant bed. Additionally, some vertical grow manufacturers claim that larger, shared beds in rack systems allow for better root systems, leading to larger yields. However, while the extra root-zone space lends itself to more developed roots, it also means each plant must share its food and water—and potential pests and diseases—with the other plants in its bed.

How They Work

Vertical grow systems work the same way horizontal systems do, as the principals of horticultural are constant. Rather, it is the logistics that change with the footprint of the system in the room. The smaller footprint, which can range in size from 6 to 8 feet in diameter for cylindrical units or can wrap around the room for wall units, allows for more garden space in a single room as all the area is utilized, from floor to ceiling.

This is why many of the original (as well as some current) vertical grow systems deploy a cylindrical shape, as this allows for several units to be placed in a single room. And because there is no space lost to overhead lighting, all the space from floor to ceiling is dedicated to plant canopy. In cylindrical systems such as the well-known Coliseum, plants are placed in netted pot containers held in place by plastic tiers, angled slightly downward toward the center light channel. Behind the tiers is a thick wall that can hold spray misters, foggers or irrigation tubes for drip lines. At the bottom of the system are larger reservoirs to catch the runoff, just like hydroponic table systems.

Other systems can be more of a hybrid between a cylindrical system and a wall system. Wall systems use either premade wall frames or the walls of a room to attach hanging grow systems. The EcoSystem, for example, uses a cylindrical plant arrangement with vertical lights down a center channel and doors that swing open to provide access to the grow chamber. However, instead of housing the system mechanics within its chamber walls, growers attach slabs of rockwool, hung vertically around the sides, to grow their plants. Spaghetti lines run directly to the medium, and the vertical chamber is run as a top-feed hydroponic system.

Other vertical grow systems abandon the cylindrical geometry altogether and use structural walls, stackable racks or premade elements such as metal-pole frames from which to hang vertical grow systems. These systems range from NFT (nutrient film technique) and top-feed hydro systems to root mister/aeroponic systems. Normally, wall systems utilize narrow trays or troughs hung in a square arrangement on three or four walls with lights hanging vertically down the center, the same as cylindrical grow systems. All of these systems, whether square or cylindrical in design, do better with hydroponics rather than with soil systems, and each utilizes standard reservoirs and pump systems to deliver water and nutrients to plant sites.

Walls of Green

Aside from the physical characteristics that vertical grow systems share, they also utilize common grow theories and techniques. In almost every vertical grow system—and especially in cylindrical units—a “sea of green” (SOG) technique must be utilized.

SOG gardens comprise many smaller plants, rather than fewer larger plants. This style of growing was developed primarily for indoor and greenhouse growers who have less space to work with than outdoor farmers. In theory, having many smaller plants is a way to mitigate the smaller yields when not growing huge trees outdoors that can produce several pounds of cannabis each. Instead, indoor growers cultivate hundreds of densely packed smaller plants that, when taken as a sum, can actually yield as much or more than an outdoor garden (and with a few more harvests per year to boot).

In SOG gardens, plants are propagated either from seeds or cloning and then allowed to develop roots and vegetate for a week or two, and then moved right into flowering, thereby keeping plant size much smaller. To aid in this technique, cannabis growers keep internode lengths shorter, which is the distance between branches on the main stem. Having shorter internode lengths means more branching, which leads to more flowering sites for budding and better plant yields.

To do this, growers use bulbs heavier in the blue spectrum, which helps plants develop good branch stacking and keeps them squat and bushy. During the initial propagation phase and before transplanting into a vertical grow system, growers keep nursery plants under fluorescent bulbs, which emit light from the blue spectrum. These lamps also use less power and run extremely cool, allowing plants to remain very close to the light source.

Once the plants are ready to vegetate, growers will utilize metal-halide (MH) bulbs for the veg cycle. MH bulbs are much heavier in the blue spectrum than high-pressure sodium (HPS) bulbs, which are used during the flowering cycle.

Growing Up

While the most compelling argument for vertical grow systems is the increased efficiency in vertically integrated, 360-degree lighting, as well as the smart use of growroom space, some of today’s more modern vertical grow systems have inexplicably abandoned the vertical lighting element. Whereas cylindrical and wall-based systems continue to utilize vertical lights with the surrounding garden, some rack systems in use at large-format, commercial-grow facilities utilize vertical space simply by using racks to stack trays and lights, one on top of another, with several layers of trays and lights in each vertical column.

While these rack systems tend to maximize space, they are less effective in maximizing the efficiency of lighting systems. One likely culprit for the dismissal of vertically integrated high-intensity discharge (HID) lighting is the growing popularity of LED lamps. While these lighting systems offer convenience in size, energy consumption and reduced heat by-product, they lack in both light quality (spectrum) and quantity (strength), thereby lowering yields significantly.

However, newer LED models have begun to offset these factors by increasing both spectral range and light intensity. Still, these units are costly and bulky, and they lack many of the typical advantages associated with LEDs such as low power draw and heat emission. Still, some newer LED units are being fashioned to fit into vertical rack systems, but at a much higher cost, with the counterargument being they save money in the long run by not needing to be replaced nearly as often as HID systems. Other rack systems feature banks of fluorescent lamps, especially in nurseries, while large rack systems utilize HID lamps hung overhead with two or three levels of garden beds. The latter option is only realistic for large warehouses with high ceilings.

Another problematic issue shared by most vertical grow systems is the difficulty posed by bulb-to-canopy distance. Traditional gardens, as well as some large-format rack systems, that use overhead hanging lights can be adjusted to maintain the distance between light and canopy as the plants grow taller. But in vertical grow systems, where the lighting systems are stationary, growers must take extra care to ensure that lights are kept cool to touch, so that as plants grow closer to the light source they do not suffer light burn or overheating.

Keeping the bulb-to-canopy distance consistent throughout a plant’s life cycle provides for more a natural and stable grow environment, a benefit that is often lost in vertical grow systems. In vertical systems with stationary light systems, the distance from bulb to plant inevitably changes as the plant grows and changes shape. This can cause problems in a plant’s physiological development and biorhythm. This is why it is important for growers to choose strains that grow short and squat and to pay close attention to how they raise their young seedlings and clones through the vegetative stage. Plants that remain squat will do much better in vertical grow systems with a fixed bulb-to-canopy distance.

Making Up the Difference

In order to work well with the height limitation on plant growth and the impact it might have on yields, good vertical grow systems offer the ability for plants to develop expansive root systems. As a complement to the SOG technique, vertical growers should choose systems that offer ample space for a garden’s root zone.

The root structure acts as energy storage for the plant. While the plant is creating food (glucose) during the light cycle via photosynthesis, the roots are storing that energy for use during the dark cycles and for developing buds during the flowering cycle. The size of the root structure is directly proportional to the yield potential of each plant.

Vertical grow systems utilizing fixed medium sizes such as rockwool slabs may limit the garden’s ability for larger yields. Many of the most successful vertical grow systems utilize open-air walls, allowing for extensive root systems to grow out from each plant site and down throughout the back side of the system, sometimes reaching the reservoir or floor at the bottom of the chamber.

Other mediums that limit root growth are not as desirable as well. Plant sites that use netted pots and allow roots to grow out into the air will be more successful in terms of yield than a system which limits root growth either by limited medium volume or too much medium. Packing a cylindrical unit with a soil or soilless medium not only affects where the roots can grow, but it also significantly cuts down on oxygen in the root zone, which roots need to grow healthy and strong.

Five Important Considerations for Vertical Grows

By Hue Gielder

There are essentially five issues to keep in mind that the heedless grower will quickly discover about vertical grows. Knowing them in advance will improve system design and results.

Clean Your Dirty Pipes: Reservoirs should always be fully clean in order to guarantee that your plants are not being fed garbage (salt buildup, algae, etc.). System designers who would prefer to automate their watering should expect to replace all plumbing between the reservoir and spigots every few cycles in order to ensure a clean delivery of nutrients and desired biologicals. To facilitate this, use as much low-cost flexible tubing as you can. Also, when dealing with vertical hydro systems, it is important to note that pinching irrigation lines can severely impact a system’s water pressure. This is especially true with a vertical “backbone” pipe, where lessening the width of tubing (for example, via T-joints or clamp valves) beyond most pumps’ half-to-full-inch output will limit the pressure seen at each vertical grow tier incrementally, as the water ascends. It’s best to reduce the line width at the actual spigots (if absolutely necessary) and abide by the pump manufacturer’s recommendations when pumping vertically.

Ditch the Dirt on the Dank: When growing vertically, there is always a risk that fluids or wet media will spill over onto mature or otherwise innocent buds below. Whether or not this is an issue will largely be determined by the watering system’s throughput and the medium’s rate of fluid absorption, as well as how the tiers of grow sites are stacked. Shared beds filled with soil will drain better by adding perlite, while hydroton (HEC) may be too heavy for some shared-bed systems.

Are You Penetrating Your Canopy? All plants prefer to be isolated and alone so that they can hoard all of the resources they desire. When growing plants within a confined space, anything that can be done to penetrate the canopy in an even manner in terms of light, carbon dioxide and fresh-air exchange will maximize individual plant health and yields.

T5s vs. Light Skirts: Plants need evenly distributed low-intensity lighting during transplant to minimize transplant shock. Shade cloths can be wrapped like skirts around grow lights or tubes, but this plastic material also easily melts. To avoid melting plastic and potential house fires, the vertical grower can create a ring out of electrical conduit or non-electrical flex wire to wrap the shade cloth around and drape down the lighting tube. However, this approach may not block sufficient light to fully eliminate transplant stress if a grower is firing numerous bulbs of high wattage. An alternative approach is to strap fluorescent T5s to the light tubes for the purpose of maintaining the proper photoperiod during transplant with much less light intensity (not to mention pretty broad spectrum as well).

How Hard Is It to Swap Your Spectrum? Vertical growers use light tubes to move bulb heat up and out of the room before it can affect canopy temperature. However, chains of lights in glass tubes can greatly complicate the swap of bulbs that frequently accompany the switch to flower. The problem is that light tubes are generally not designed for ease of access. When connecting together individual light tubes to create a single light string, it’s recommended that the grower pay special attention to the creation of a custom system of access that is convenient for maintenance. Attaching light tubes to rails of light movers so that they can slide in and out of vertical systems is a good idea. Another consideration is to fully veg plants before transplanting them into vertical systems and give them only a few days of veg cycle (using your HPS bulbs) before flipping to the 12/12 flowering stage.